DAFWA Esperance senior research officer Mark Seymour inspects the hybrid canola nitrogen management trial at Grass Patch in 2012.
Improved hybrid genetics are allowing growers in low-rainfall areas to better match nitrogen applications to yield potential in canola crops as the season unfolds.
This is making Roundup Ready® (RR) hybrid varieties worth the risk of higher seed costs in mallee areas and a profitable break-crop option.
Trials at Grass Patch, near Esperance, during the past two years have shown that RR hybrids are standout performers in efficient nitrogen use and economic returns compared with open-pollinated varieties and triazine-tolerant (TT) hybrids, as highlighted in Figures 1 and 2.
The trials, which are continuing this year, are an initiative of the Department of Agriculture and Food, Western Australia (DAFWA), and were funded last year by the GRDC’s Esperance zone Regional Cropping Solutions Network (RCSN).
Research by DAFWA at the Grass Patch site found the grain yield of hybrid RR canola lines continued to respond to nitrogen applications up to 12 weeks after sowing, while open-pollinated TT lines responded up to eight weeks after sowing.
Hybrid Roundup Ready® canola lines outperformed open pollinated varieties in yield, oil and returns at the trial site at Grass Patch.
When the hybrid RR varieties received less than 25 kilograms of nitrogen per hectare, they also had equal or better yields and returns than the open-pollinated RR lines and all the TT lines that received more nitrogen.
DAFWA Esperance senior research officer Mark Seymour says the results indicated hybrid RR lines could provide opportunities for growers in the region to use low rates of nitrogen at seeding, then monitor the season and add more nitrogen as needed to reach optimal yield.
“These new cultivars could change nutrition management in low-rainfall areas and enable canola crops to be a more profitable part of the rotation,” he says.
“Our aim is to provide growers with more accurate guidelines for optimal nitrogen rates and times of application to maximise grain and oil yields from these crops.”
The results will also feed into a five-year GRDC and DAFWA break-crop agronomy project that starts this year and has a major focus on timing of nitrogen applications in canola.
FIGURE 1 Mean grain yield (kg/ha, averaged over same N rates and time of application) of six canola varieties at Grass Patch in 2012.
FIGURE 2 Mean net return ($/ha, averaged over same N rates and time of application) of six canola varieties at Grass Patch in 2012.
Mr Seymour says the Grass Patch trial indicated staggered strategies for nitrogen application in hybrid RR canola and CB™ Telfer TT canola could pay off.
“We found little difference in yield or return from applying nitrogen at seeding, at four weeks or at eight weeks in these lines,” he says.
“In DAFWA trials planned for 2013 we will target timing of nitrogen in low-rainfall areas right throughout WA – particularly at rates of nitrogen at or below 50kg/ha.” Mr Seymour says nitrogen decision-support tools will help growers optimise nitrogen rates for expected crop yields as the season develops.
“Using these tools can help to better match inputs to soil and seasonal conditions,” he says.
For example, the Grass Patch trial site had 70kg N/ha available in the soil at sowing last year, which was sufficient to produce about 900kg/ha of canola.
Mr Seymour says if the target yield in this low-rainfall area is 1.2 tonnes/ha, the reasonable expectation for that year was a grain yield response to a further 25kg N/ha.
The trials showed that applying more might have reduced oil and returns.
There is a range of tools available for calculating soil nitrogen and Mr Seymour uses SYN (Select Your Nitrogen). This is an Excel-based calculator available from DAFWA that uses soil organic carbon, rotation and soil type as inputs.
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